Case-insensitive regular expression in Java

Friday, October 9, 2015

Case-insensitive regular expression in Java

Sheng Wang 6:45 PM Java SE, Regular Expression No Comments

The java.util.regex.Pattern has several flags which are very helpful. One of them is CASE_INSENSITIVE

Just add this flag when creating pattern instance. Everything else follows normal regex usage.

Here is a hello world level demo for case-insensitive regular expression in Java.

package com.shengwang.demo;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class RegexCaseInsensitive {
 
  public static void main(String[] args) {
    String input = "ABC";
    String regex = "abc";
    boolean  matchResult;
    Pattern p = Pattern.compile(regex, Pattern.CASE_INSENSITIVE); // add flag here
    Matcher m = p.matcher(input);
    matchResult = m.matches();
    System.out.println("matchResult="+matchResult); // print "matchResult=true"
  }
}

In fact case-insensitive regular expression can also be enable by add embedded flag expression(?i). But I personally prefer using Pattern.CASE_INSENSITIVE flag for code readability.

For most basic regular expression Java API usage, check out article “The basic regular expression API in Java”